The present invention relates to a semiconductor memory device having an antifuse and an antifuse programming method.
Antifuses are a known type of electrical fuses. An antifuse is typically comprised of a MOS transistor or a MOS capacitor. An antifuse is programmed by applying a high voltage between a gate electrode and diffusion layers/substrate, thereby breaking down a gate insulating film. Namely, in a programmed state, the gate electrode and the diffusion layers/substrate are short-circuited to be electrically conducted to each other. In an unprogrammed state, the gate electrode and the diffusion layers/substrate remain electrically unconductive to each other. The element is electrically off before being programmed and electrically on after being programmed, so that it is called an antifuse. Data can be read out from the antifuse by determining whether a read current (cell current) flows between the gate electrode and the diffusion layers.
Among the antifuse-related documents, there are, for example, U.S. Pat. No. 7,253,496 and Japanese Unexamined Patent Application Publications Nos. 2009-259385, 2009-276764, and 2009-277291.